Most modern water heaters are constructed of a steel tank with a glass lining. Passive anode rods are a vital component to water heaters utilizing a steel tank or other forms of tanks susceptible to corrosion. An anode rod can act as a sacrificial anode that provides protection against tank corrosion. In particular, the anode rod acts as a sacrificial anode by way of galvanic corrosion.
As a result of the galvanic corrosion, a galvanic current can flow from the anode rod to a cathode to which the anode rod is electrically connected. The cathode is commonly the exterior of the tank connected to an earth ground. As the galvanic current is a result of the galvanic corrosion, greater corrosion results in greater galvanic current and vice versa.
An undesirable side effect of the use of an anode rod is an unpleasant smell, similar to rotten eggs. In particular, hydrogen can be produced as a byproduct of the galvanic reaction. The combined presence of hydrogen, sulfur, and sulfur-reducing bacteria can result in hydrogen sulfide. Such hydrogen sulfide can emit the unpleasant sulfurous smell, similar to rotten eggs, when water is used from the water heater. In particular, magnesium or magnesium alloy anode rods can result in a greater accumulation of hydrogen sulfide than aluminum or aluminum/zinc rods as the magnesium rods are more reactive (i.e. more susceptible to galvanic corrosion) under certain water conditions.
Therefore, a partial solution to the problem of sulfurous smell can be to replace a magnesium anode rod with an aluminum/zinc anode rod. However, for owners of a water heater that already have magnesium rods, replacement represents an undesirable additional monetary expense and loss of time. Further, for water with particular characteristics, such as softened water which can increase galvanic corrosion, even use of a less reactive aluminum/zinc rod does not solve the problem.
Powered anode rods which provide electricity into the tank can be used to completely replace sacrificial anodes. However, such powered rods are often quite expensive and much more complex for a homeowner to install and operate. Therefore, powered anode rods are generally undesirable for inclusion in standard model appliance production.
Another potential solution can be to periodically flush the water heater of all water, sanitize, and replace with fresh water. However, this again represents an undesirable use of time and further can result in leaks or even a complete release of water into a home if the proper order of flushing steps is not followed.
A more drastic solution to the problem of sulfurous smell is to remove the anode rod completely. While this may result in less undesirable smell, it also results in large amounts of tank corrosion. In particular, anode rods are essential to combating tank corrosion. Thus, complete removal of the anode rod will certainly lead to tank damage, drastically shortening the lifespan of the water heater.
As another exemplary problem, often the anode rod provided for a water heater is oversized, such that an excessively large magnitude of surface area is provided. Therefore, unnecessary galvanic action can occur which unnecessarily corrodes the anode rod and causes excess smell in the event sulfur is present.
Therefore, systems and methods for adjusting the rate of anode rod galvanic corrosion are desirable. In particular, systems and methods that adjust the rate of anode rod corrosion while maintaining a minimum rate such that the tank is properly protected from corrosion are desirable.